Sealed batteries are well known in the art and typically include a relief/check valve for venting gases generated within the cell compartment when the internal pressure exceeds a predetermined super atmospheric level. Nickel-zinc batteries, for example, commonly operate with a positive internal pressure of about one-half pound per square inch or more to promote oxygen recombination within the battery and to keep CO.sub.2 in the air from contaminating the electrolyte when the pressure in the cell falls below zero psig. Similarly gas recombination type lead-acid batteries are known to operate at internal pressures ranging from about 1/2 psig to about 50 psig (i.e., depending on the particular application) to promote the oxygen recombination reaction and to exclude ambient oxygen from the battery. It is necessary for the prolonged life of such batteries that after the gases have been vented the relief/check valves close and reseal as near as possible to their opening pressure in order (1) to prevent unnecessary loss of the internal gases otherwise available for recombination and (2) to prevent any influx of ambient atmosphere into the battery as the internal pressure within the battery falls.
Sealed batteries have heretofore used relief/check valves employing a single valve member which controls the venting pressure of the battery and which is relied on to reseal the cell compartment when the pressure in the compartment falls below the venting (i.e. valve opening) pressure. In practice, however, some such single member valves do not actually reseal again until pressures as low as 25% or less of their opening pressure are reached. In fact, some such valves tested by Applicant's assignee did not reseal until the pressure in the battery had dropped below zero psig. No commercially available battery relief/check valve has been found which provides effective resealing near the opening pressure.
Accordingly, it is an object of the present invention to provide a unique relief/check valve with independent venting and sealing members for venting an electric storage battery at a predetermined superatmospheric venting pressure and resealing it at pressures at or near the venting pressure. This and other objects and advantages of the present invention will become more readily apparent from the detailed description thereof which follows.